1. Field of the Invention
The present invention relates to the termination of telephone calls in a telephone network that provides privacy screening to its subscribers.
2. Background of the Invention
Private telephone numbers are telephone numbers that block services such as “caller ID” that would otherwise identify the caller to the party he or she is calling (the “called party”). A privacy screening service is a service that allows the subscriber to screen incoming calls. For example, a subscriber can choose to accept or reject an unknown call. In a telephone systems that offers private numbers and a privacy screening service to its subscribers, calls from a private number to a subscriber with the privacy screening service cannot be completed automatically, unless the caller grants permission to the system allowing the system to override the privacy of his or her number.
FIG. 1 is a schematic diagram showing the basic architecture of an Advanced Intelligent Network telephone system. The Advanced Intelligent Network System is described in U.S. Pat. Nos. 5,701,301 and 5,838,774, which are hereby incorporated by reference. FIG. 1 shows the caller's telephone 101 which is connected via voice line 102a to its Service Switching Point (SSP) 103. SSP 103 is connected via voice trunk 102b to a second SSP (SSP 104). SSP 104 is the SSP that services the called party's telephone 105. In this example, the called party is a subscriber who has subscribed to the privacy screening service. (The called party will be referred to as the “subscriber” as well as the “called party” herein.) FIG. 1 also shows a Signaling Transfer Point (STP) 106 which services a Service Control Point (SCP) 107 and a third SSP (SSP 108) 108 which services a Service Node (SN) 109. SCP 107 has a database 107a which contains subscriber information.
STP 106 is a signaling hub that routes packets of data over the common channel signaling network. Signaling System 7 (SS7) is the protocol that runs over the common channel signaling network. The common channel signaling network using the Signaling System 7 protocol is commonly referred to as the SS7 network. The SS7 network carries data and control messages to the SSPs in the telephone network. SCPs are powerful fault-tolerant computers, e.g., AT&T Star Server FT Model 3200 or AT&T Star Server FT Model 3300 computers (these computers and more recent models such as the Advantage P200 and the Advantage 4P200 are available from Lucent Technologies). SCPs are “intelligence centers” with access to applications packages, software, routines and databases that enable the network to deliver advanced services such as caller ID, privacy screening and call forwarding. SNs are physically generally similar to SCPs, but include voice and Dual Tone Multi-Frequency (DTMF) signal recognition circuits and voice synthesizers. The operators of the telephone network can write software routines so that their SNs can manage data, perform digit collection, respond to calls, route calls as specified by the telephone network, and perform voice recognition functions. The SN's voice circuits can be programmed to provide a voice response (e.g., to play pre-selected announcements) to callers. The SN can also be programmed to respond to input from the callers by, e.g., further routing the call.
As shown in FIG. 1, STP 106 controls communications between SSPs 103, 104 and 108 and SCP 107 over the SS7 data links. The SSPs are connected to the caller's and the subscriber's telephones and to each other via voice lines 102a and 102c and via voice trunks 102b and 102d. The SSPs can also communicate with each other over the SS7 data links shown in FIG. 1. The SSPs are also connected to and communicate with STP 106 and SCP 107 via SS7 data links 110a, 110b, 110c and 110d. SN 109 is connected to SSP 108 by an Integrated Service Digital Network (ISDN) Basic Rate Interface (BRI) line 111. Although FIGS. 1-2c only show one SCP and one STP, SCP 107 and STP 106 in FIGS. 1-2c generally represent two redundant SCPs and STPs, respectively, because it is preferable to have redundant SCPs and STPs in an AIN system.
FIG. 1a illustrates a prior art system for routing calls to subscribers to a privacy screening service. When a caller places a call to the subscriber, the call is routed by SSP 103 to SSP 104. FIG. 1a shows call 1 routed from the caller to SSP 103 and then to SSP 104. Because the subscriber has subscribed to the privacy screening service, that call (like all calls to that subscriber's number) triggers a “termination attempt trigger” or TAT. In response to the TAT, SSP 104 issues query 2, shown in FIG. 1a. Query 2 is a message that goes up to SCP 107 asking for directions as to how the call should be terminated. The query includes the following information: the subscriber's telephone number (in the called party field), the caller's telephone number (in the calling party field), the trigger criteria type (indicating the service for which the query is intended) and a presentation indicator in the calling party ID field.
SCP 107 checks the calling party's presentation indicator in the calling party ID field, and determines whether that caller has a public number (i.e., it is not a private number) or a private number, or whether the caller is unknown. If the caller's number is known and public, SCP 107 sends back a response (response 3 in FIG. 1a) instructing SSP 104 to terminate the call, and to supply the caller's telephone number (and if the subscriber has subscribed to a higher level of service, the caller's name and telephone number). In that case, SSP 104 terminates the call (call 1′ in FIG. 1a), i.e., completes the call, supplying the subscriber with the caller's number (and possibly also with the caller's name if the subscriber has subscribed to, e.g. caller ID deluxe which provides the caller's name as well as the caller's telephone number).
However, if the caller's number is private, SCP 107 cannot authorize termination of the call without permission from the caller. In that case, the SCP's response (response 3 in FIG. 1a) directs the call from SSP 104 to SN 109 via SSP 108 (call 4 in FIG. 1a). Under the standard AIN protocol BRI Q.931, the call carries with it three numbers: (1) the number of the original called party (in this case the subscriber); (2) the number of the re-directing party (also the subscriber in this case); and (3) the number of the calling party. SN 109 then engages in a dialog with the caller. SN 109 asks the caller for permission to override his/her privacy. The caller is asked whether he or she agrees to have his or her privacy overriden. If the caller answers yes (e.g., by pressing 1 on his or her telephone), SN 109 dials a Customized Dialing Plan (CDP) code followed by the calling party number and the called party number (call 7 in FIG. 1a). The CDP code triggers an Info_Analyzed query to SCP 107 (query 5 in FIG. 1a). SCP 107 then retrieves the calling party number and the called party number from the query, and responds by sending an Analyze_Route message (response 6 in FIG. 1a) to SSP 108, with the subscriber's number as the called party number. SSP 108 makes an outbound call (call 7′ in FIG. 1a) to the subscriber's SSP 104. The number of the actual calling party is substituted in the calling party field.
This call triggers a second TAT query at SSP 104 to SCP 107 (query 8), asking for authorization to terminate the call to the subscriber. SCP 107 recognizes this call as originating from an SN, and accordingly responds (response 9) authorizing termination of the call to the subscriber (call 1′ in FIG. 1a), and release of the calling party's number, so that the subscriber can accept or reject the call.
However, the subscriber's line is also sometimes marked private. In that case, the SN does not have the subscriber's telephone number, because BRI lines do not have access to the re-directing party number when a call is being forwarded from a private number (this is generally true for all systems using the AIN Release 0.0 architecture). Thus SN 109 cannot place call 7 back to the subscriber, because SN 109 no longer knows the subscriber's telephone number.
Thus this system cannot terminate calls when both the calling party and the subscriber have private numbers, because the subscriber's telephone number is no longer available when the SN tries to re-route the call to the subscriber.